The solar heating system component is adapted for use in connection with a closed solar energy collecting system including a primary system for absorbing heat energy from the sun by means of solar collectors through which flow a primary fluid which is heated and then circulated to a surge tank which also includes heat exchange means. Heat is transferred from the primary fluid to a secondary fluid which flows in a secondary circuit and is used for purposes such as to supply warm water, space heating or cooling and the like.
In theory, the secondary fluid could be heated directly in the solar collectors thereby eliminating the necessity for two circuits. However, in practice, it is usually advisable to provide two circuits, one connected to the solar collectors in which the fluid includes an anti-freeze or corrosion inhibitor while in the other circuit it is usually advisable to circulate substantially pure water. It is therefore necessary to provide heat exchange means between two such circuits in order to transfer heat from the solar collector system to the ultimate use system.
The system which circulates fluid through the solar collector means is a closed system. As a consequence, an expansion tank is required to accommodate expansion and contraction of the fluid in the circuit which is caused by temperature changes. It is also necessary to provide a pressure relief valve in such a system as well as a valve to manually adjust the amount of air in the expansion tank. The system must also have a filling valve and the necessary means to pump fluid therethrough. Such a system constitutes very much the standard hydronic system as commonly used for heating and also adapted for use in solar energy collecting systems.
In addition to all of the above-mentioned components as used in a standard hydronic system, the previously described solar system also requires heat exchange means. A differential thermostat should also be connected with sensors at two points in the system to discontinue heat exchange between fluids in the primary and secondary circuits when the temperature of the fluid in the secondary circuit approaches the temperature of the fluid in the primary circuit.
The assembling and connecting all of the components necessary for the above-described fluid systems as is currently done is time consuming in the field. Also, there is a costly duplication in that separate tanks are used to house a heat exchanger and an expansion tank. Further, there is a duplication of plumbing fittings used in connecting all of the valves and other components.
The present invention provides a combined heat exchanger-expansion tank component to which pumps may be attached with pipe fittings as well as a relief valve and sight glass means to determine air volume. Additionally, a differential thermostat may be mounted on the combined heat exchanger-expansion tank so that motors may be factory wired to the differential thermostat. The tank itself can also be factory insulated.
The present invention results in greatly reduced overall cost and also makes possible much less field installation work than has previously been necessary. Factory pre-engineered and fabricated assembly also insures a more satisfactory operating system. The combination provides a convenient location for checking anti-freeze or corrosion inhibitor and the amount of air or fluid serving the system.